cuda-samples/Samples/simpleAttributes/simpleAttributes.cu

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// includes, system
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

// includes CUDA
#include <cuda_runtime.h>

// includes, project
#include <helper_cuda.h>
#include <helper_functions.h>  // helper functions for SDK examples

////////////////////////////////////////////////////////////////////////////////
// declaration, forward
void runTest(int argc, char **argv);

cudaAccessPolicyWindow initAccessPolicyWindow(void) {
  cudaAccessPolicyWindow accessPolicyWindow = {0};
  accessPolicyWindow.base_ptr = (void *)0;
  accessPolicyWindow.num_bytes = 0;
  accessPolicyWindow.hitRatio = 0.f;
  accessPolicyWindow.hitProp = cudaAccessPropertyNormal;
  accessPolicyWindow.missProp = cudaAccessPropertyStreaming;
  return accessPolicyWindow;
}

////////////////////////////////////////////////////////////////////////////////
//! Simple test kernel for device functionality
//! @param data  input data in global memory
//! @param dataSize  input data size
//! @param bigData  input bigData in global memory
//! @param bigDataSize  input bigData size
//! @param hitcount how many data access are done within block
////////////////////////////////////////////////////////////////////////////////
static __global__ void kernCacheSegmentTest(int *data, int dataSize, int *trash,
                                            int bigDataSize, int hitCount) {
  __shared__ unsigned int hit;
  int row = blockIdx.y * blockDim.y + threadIdx.y;
  int col = blockIdx.x * blockDim.x + threadIdx.x;
  int tID = row * blockDim.y + col;
  uint32_t psRand = tID;

  atomicExch(&hit, 0);
  __syncthreads();
  while (hit < hitCount) {
    psRand ^= psRand << 13;
    psRand ^= psRand >> 17;
    psRand ^= psRand << 5;

    int idx = tID - psRand;
    if (idx < 0) {
      idx = -idx;
    }

    if ((tID % 2) == 0) {
      data[psRand % dataSize] = data[psRand % dataSize] + data[idx % dataSize];
    } else {
      trash[psRand % bigDataSize] =
          trash[psRand % bigDataSize] + trash[idx % bigDataSize];
    }

    atomicAdd(&hit, 1);
  }
}
////////////////////////////////////////////////////////////////////////////////
// Program main
////////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv) { runTest(argc, argv); }

////////////////////////////////////////////////////////////////////////////////
//! Run a simple test for CUDA
////////////////////////////////////////////////////////////////////////////////
void runTest(int argc, char **argv) {
  bool bTestResult = true;
  cudaAccessPolicyWindow accessPolicyWindow;
  cudaDeviceProp deviceProp;
  cudaStreamAttrValue streamAttrValue;
  cudaStream_t stream;
  cudaStreamAttrID streamAttrID;
  dim3 threads(32, 32);
  int *dataDevicePointer;
  int *dataHostPointer;
  int dataSize;
  int *bigDataDevicePointer;
  int *bigDataHostPointer;
  int bigDataSize;
  StopWatchInterface *timer = 0;

  printf("%s Starting...\n\n", argv[0]);

  // use command-line specified CUDA device, otherwise use device with highest
  // Gflops/s
  int devID = findCudaDevice(argc, (const char **)argv);
  sdkCreateTimer(&timer);
  sdkStartTimer(&timer);
  // Get device properties
  checkCudaErrors(cudaGetDeviceProperties(&deviceProp, devID));
  dim3 blocks(deviceProp.maxGridSize[1], 1);

  // Make sure device the l2 optimization
  if (deviceProp.persistingL2CacheMaxSize == 0) {
    printf(
        "Waiving execution as device %d does not support persisting L2 "
        "Caching\n",
        devID);
    exit(EXIT_WAIVED);
  }

  // Create stream to assiocate with window
  checkCudaErrors(cudaStreamCreate(&stream));

  // Set the amount of l2 cache that will be persisting to maximum the device
  // can support
  checkCudaErrors(cudaDeviceSetLimit(cudaLimitPersistingL2CacheSize,
                                     deviceProp.persistingL2CacheMaxSize));

  // Stream attribute to set
  streamAttrID = cudaStreamAttributeAccessPolicyWindow;

  // Default window
  streamAttrValue.accessPolicyWindow = initAccessPolicyWindow();
  accessPolicyWindow = initAccessPolicyWindow();

  // Allocate size of both buffers
  bigDataSize = (deviceProp.l2CacheSize * 4) / sizeof(int);
  dataSize = (deviceProp.l2CacheSize / 4) / sizeof(int);

  // Allocate data
  checkCudaErrors(cudaMallocHost(&dataHostPointer, dataSize * sizeof(int)));
  checkCudaErrors(
      cudaMallocHost(&bigDataHostPointer, bigDataSize * sizeof(int)));

  for (int i = 0; i < bigDataSize; ++i) {
    if (i < dataSize) {
      dataHostPointer[i] = i;
    }

    bigDataHostPointer[bigDataSize - i - 1] = i;
  }

  checkCudaErrors(
      cudaMalloc((void **)&dataDevicePointer, dataSize * sizeof(int)));
  checkCudaErrors(
      cudaMalloc((void **)&bigDataDevicePointer, bigDataSize * sizeof(int)));
  checkCudaErrors(cudaMemcpyAsync(dataDevicePointer, dataHostPointer,
                                  dataSize * sizeof(int),
                                  cudaMemcpyHostToDevice, stream));
  checkCudaErrors(cudaMemcpyAsync(bigDataDevicePointer, bigDataHostPointer,
                                  bigDataSize * sizeof(int),
                                  cudaMemcpyHostToDevice, stream));

  // Make a window for the buffer of interest
  accessPolicyWindow.base_ptr = (void *)dataDevicePointer;
  accessPolicyWindow.num_bytes = dataSize * sizeof(int);
  accessPolicyWindow.hitRatio = 1.f;
  accessPolicyWindow.hitProp = cudaAccessPropertyPersisting;
  accessPolicyWindow.missProp = cudaAccessPropertyNormal;
  streamAttrValue.accessPolicyWindow = accessPolicyWindow;

  // Assign window to stream
  checkCudaErrors(
      cudaStreamSetAttribute(stream, streamAttrID, &streamAttrValue));

  // Demote any previous persisting lines
  checkCudaErrors(cudaCtxResetPersistingL2Cache());

  checkCudaErrors(cudaStreamSynchronize(stream));
  kernCacheSegmentTest<<<blocks, threads, 0, stream>>>(
      dataDevicePointer, dataSize, bigDataDevicePointer, bigDataSize, 0xAFFFF);

  checkCudaErrors(cudaStreamSynchronize(stream));
  // check if kernel execution generated and error
  getLastCudaError("Kernel execution failed");

  // Free memory
  checkCudaErrors(cudaFreeHost(dataHostPointer));
  checkCudaErrors(cudaFreeHost(bigDataHostPointer));
  checkCudaErrors(cudaFree(dataDevicePointer));
  checkCudaErrors(cudaFree(bigDataDevicePointer));

  sdkStopTimer(&timer);
  printf("Processing time: %f (ms)\n", sdkGetTimerValue(&timer));
  sdkDeleteTimer(&timer);

  exit(bTestResult ? EXIT_SUCCESS : EXIT_FAILURE);
}